ep the dog
and the cats."

CHAPTER X

OTHER DISEASES, MOSTLY TROPICAL, KNOWN OR THOUGHT TO BE TRANSMITTED BY
INSECTS

SLEEPING SICKNESS

One of the worst scourges of Africa and one that is to-day attracting
world-wide attention is the disease known as trypanosomiasis, the
terminal phase of which is sleeping sickness, one of the most ghastly
diseases that we know.

Among the Protozoa referred to in one of the earlier chapters mention
was made of certain trypanosomes which inhabit the blood of man and
certain animals. Very little was known concerning these parasites
previous to the beginning of the present century, but since that time
several have been found to be of great economic importance. The group is
being studied extensively and every day our knowledge of them is
increasing so that we now know quite definitely the life-history of
several.

_Trypanosoma lewisi_, a parasite of rats, is perhaps the best known as
it is always common where-ever rats are found. Sometimes as many as 30%
or 40% of the rats of certain districts are infected. It is thought that
these are transmitted from rat to rat by the common rat-louse which
serves as an intermediate host. Fleas may also act as disseminating
agents.

A few other kinds cause serious disease of animals, but we are more
interested just now in the particular one that is causing so much
trouble in Africa. This parasite was discovered in 1902 and was named
_Trypanosoma gambiensi_ (Fig. 111). Since then it has been found to be
widely distributed. Although the natives have doubtless long been
subject to the disease caused by this parasite, the recent influx of
whites to these regions and the consequent movements of the natives have
caused a great spread of the disease so that whole regions are now made
desolate, the inhabitants dying or fleeing to escape the uncanny death.

The disease may run its course in a few months or it may take years. The
symptoms are various, but infection is usually soon followed by fevers,
sometimes mild, sometimes severe, which recur at irregular intervals.
Certain glands or other parts of the body may become swollen. More or
less extensive skin eruptions occur on all parts of the body and the
patient gradually becomes anemic and physically and intellectually
feeble. The nervous system seems to be affected by the parasite, either
directly or by the action of the toxins it produces. The patient becomes
more debilitated and moros